C++ solutions (sorting, maps and sets).

• ``````bool containsDuplicate1(vector<int>& nums) {
sort(nums.begin(), nums.end());
for (int i=0; i<int(nums.size())-1; i++) {
if (nums[i]==nums[i+1])
return true;
}
return false;
}

bool containsDuplicate2(vector<int>& nums) {
map<int, bool> myMap;
// unordered_map<int, bool> myMap;
for (auto& num: nums) {
if (myMap.find(num) != myMap.end())
return true;
else
myMap[num] = true;
}
return false;
}

bool containsDuplicate3(vector<int>& nums) {
multimap<int, bool> myMap;
// unordered_multimap<int, bool> myMap;
for (auto& num: nums) {
if (myMap.find(num) != myMap.end())
return true;
myMap.insert(make_pair(num, true));
}
return false;
}

bool containsDuplicate4(vector<int>& nums) {
set<int> mySet;
// unordered_set<int> mySet;
// multiset<int> mySet;
// unordered_multiset<int> mySet;
for (auto& num: nums) {
if (mySet.find(num) != mySet.end())
return true;
mySet.insert(num);
}
return false;
}``````

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